Synthesis and Structure of Bis(diphenylphosphinimino)methanide and

Article pubs.acs.org/Organometallics

Synthesis and Structure of Bis(diphenylphosphinimino)methanide and Bis(diphenylphosphinimino)methanediide Beryllium Complexes Melike Bayram, Dominik Naglav, Christoph Wölper, and Stephan Schulz* Institute of Inorganic Chemistry, University of Duisburg-Essen, 45117 Essen, Germany S Supporting Information *

ABSTRACT: Reactions of BeEt2 with bis(diphenylphosphinimino)methanes H2C[PPh2NR]2 yielded the first bis(diphenylphosphinimino)methanide and bis(diphenylphosphinimino)methanediide beryllium complexes [CH(PPh2N-2,6-i-Pr2C6H3)2]BeEt (1), [C(PPh2NSiMe3)2](BeEt)2 (2), and [C(PPh2NPh)2](BeEt)2 (3), respectively. 1−3 were characterized by multinuclear NMR and IR spectroscopy as well as single-crystal X-ray diffraction.

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INTRODUCTION The chemistry of beryllium differs significantly from that of the heavier group 2 metals as well as from group 12 metalsin particular from the well-established Mg and Zn chemistrydue to the small size of the Be atom and its high Lewis acidity. Even though the high toxicity of beryllium and beryllium compounds has hampered Be compounds from becoming widely applied,1 beryllium chemistry has received growing interest within the past decade.2 In addition to well-established Cp-substituted beryllium complexes, which were initially reported by Fischer in 19593 and whose structures in the solid state,4 in solution4h,5 and in the gas phase,6 respectively, have been studied by experimental means and by quantum chemical calculations,7 homoleptic and heteroleptic complexes with sterically demanding substituents have been investigated. Power et al. reported on Be complexes containing terphenyl ligands,8 while the synthesis, structure, and reactivity of base-stabilized beryllium complexes, in particular NHC-coordinated beryllium compounds,9 was studied by several groups. In addition, the search for isolable Be(I) compounds as well as highly electrophilic cationic complexes, for which quantum chemical calculations have become very important,10 has pushed this chemistry forward in the last few years. Bidentate and tridentate N-chelating organic substituents such as amidinates, guanidinates, β-diketiminate, bis(phosphinimino)methanide, and tris(pyrazolyl)borate have been established for the synthesis of stable Mg(I) and Zn(I) complexes in the past.11 As a consequence, heteroleptic beryllium complexes containing amidinate,12 β-diketiminate,13 and tris(pyrazolyl)borate substituents,14 which are potential precursors for the corresponding Be(I) complexes, have been synthesized and structurally characterized, whereas bis(phosphinimino)methanide beryllium complexes are unknown, to date. Unfortunately, to the best of our knowledge, all complexes failed for the synthesis of the desired monovalent beryllium complexes. © XXXX American Chemical Society

Due to our general interest in main-group-metal chemistry, we started only recently our research on beryllium compounds and reported on the synthesis of several heteroleptic and homoleptic beryllium complexes containing Cp* 15 and tris(pyrazolyl)borate16 as well as amide substituents.17 We herein report o n r eactions of BeEt 2 with bis(diphenylphosphinimino)methanes of the general type H2C[PPh2NR]2 in different molar ratios, yielding the first mononuclear bis(diphenylphosphinimino)methanide as well as dinuclear bis(diphenylphosphinimino)methanediide beryllium complexes.

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RESULTS AND DISCUSSION Equimolar reactions of H2C[PPh2NR]2 (R = SiMe3, Ph, 2,6-iPr2C6H3) with BeEt2 at −78 °C occurred with elimination of ethane, as was shown by in situ 1H NMR spectroscopy (Scheme 1). Scheme 1. Synthesis of 1

Unfortunately, only the reaction with H2C(PPh2N-2,6-iPr2C6H3)2 resulted in the quantitative formation of [CH(PPh2N-2,6-i-Pr2C6H3)2]BeEt (1), which is a stable compound at ambient temperature in solution and in the solid state. In contrast, reactions of BeEt2 with H2C[PPh2NR]2 (R = SiMe3, Ph) in different molar ratios (2:1, 1:1, 1:2) without exception Received: May 11, 2016

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DOI: 10.1021/acs.organomet.6b00380 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

(1.6373(12), 1.6373(11) Å) and P−C bond lengths (1.6954(14), 1.6874(14) Å) as well as the endocyclic P−C− P (129.53(8)°) and C−P−N bond angles (109.26(6), 110.63(7)°) within the CP2N2Be metallcycle of 1 are comparable to those reported for other bis(phosphinimino)methanide metal complexes.20 In comparison to the endocyclic N−Be−N (108−117°) and C−N−Be (117−123°) bond angles observed in β-diketiminate beryllium complexes, the N−Be−N (117.35(12)°) and P−N−Be bond angles (124.16(10), 124.52(9)°) of 1 are relatively large (Table 1).

gave mixtures of the expected bis(diphenylphosphinimino)methanide complexes [CH(PPh2NSiMe3)2]BeEt and [CH(PPh2NPh)2]BeEt, respectively, which were clearly identified by in situ 1H NMR spectroscopy studies, as well as nonreacted H2C[PPh2NR]2 and insoluble precipitates. Filtering off the precipitates gave clear solutions, which were found to decompose at ambient temperature within 1−2 days with subsequent formation of additional insoluble precipitate, indicating that the bis(diphenylphosphinimino)methanide beryllium complexes are thermally unstable. Addition of Lewis bases such as thf, acetonitrile, and 4-dimethylaminopyridine (DMAP) had no stabilizing effect, indicating that 1 is not coordinated, most likely as a result of steric effects. Comparable findings were reported for the analogous lithium complex [CH(PPh2N-2,6-i-Pr2C6H3)2]Li,28e which contains a twocoordinate lithium atom. Compound 1 is soluble in toluene and THF, respectively. The 1H NMR spectrum of 1 shows the resonances of the Be-Et group at −0.24 (methylene) and 0.50 ppm (methyl) as well as the resonances of the bis(phosphinimino)methanide ligand including the backbone methine proton at 1.02 ppm in the expected 1:1 molar ratio. The 31P NMR spectrum of 1 shows one sharp singlet at 29.95 ppm, which is shifted downfield in comparison to H2C[PPh2N-2,6-i-Pr2C6H3]2 (−16.23 ppm). The IR spectrum of 1 shows a strong absorption at 1238 cm−1, which can be ascribed to the PN stretching vibration. Single crystals of 1 were obtained upon slow recrystallization from a solution of 1 in toluene at ambient temperature. 1 crystallizes in the orthorhombic space group Pbca with one independent molecule in the asymmetric unit. Figure 1 shows the solid-state structure of 1.

Table 1. Selected Bond Lengths (Å) and Angles (deg) of 1− 3 Be−N N−P P−Cbba

1

2

3

1.654(2), 1.667(2) 1.6373(12), 1.6373(11) 1.6954(14), 1.6874(14)

1.667(4), 1.667(4), 1.667(4), 1.671(4) 1.613(2), 1.626(2), 1.621(2), 1.611(2) 1.715(3), 1.714(3), 1.709(3), 1.717(3) 1.827(5), 1.828(4), 1.817(5), 1.842(5) 1.708(5), 1.739(5), 1.720(5), 1.727(5) 2.688(6), 2.563(6) 134.29(16), 133.54(17) 139.27(19), 81.97(16), 80.20(16), 123.41(18), 141.9(2), 82.13(16), 80.79(16), 123.99(19)

1.649(3), 1.646(3) 1.6352(16), 1.6418(16) 1.7143(19), 1.716(2) 1.841(3), 1.827(3) 1.721(3), 1.729(3) 2.618(4) 128.87(11)

91.9(2), 91.2(2), 91.1(2), 90.9(2) 98.15(13), 96.80(12), 97.68(13), 96.65(12) 88.22(17), 89.77(17), 88.97(17), 90.06(17) 94.7(2), 88.9(2)

89.69(15), 89.73(15) 94.72(9), 93.84(9) 91.43(12), 92.10(12)° 91.11(14)

Be−Cbb Be−Cet

1.753(2)

Be···Be P−Cbb−P

129.53(8)

P−Cbb−Be

N−Be−N N−Be−Cbb

117.35(12)°

N−P−Cbb

109.26(6), 110.63(7) 124.16(10), 124.52(9)°

P−N−Be Be−Cbb−Be a

141.52(14), 83.78(12), 82.72(12), 128.86(14)

Cbb = Cbackbone.

Despite its electron deficiency, 1 failed to react with strong Lewis bases such as dmap, pyridine, and acetonitrile with formation of the corresponding base-coordinated complexes as was found for the analogous lithium complex,28e most likely resulting from the effective shielding of the electron-deficient Be atom by the sterically demanding 2,6-i-Pr2C6H3 (Dipp) substituents. We then became interested in 2-fold deprotonation reactions of bis(diphenylphosphinimino)methanes H2C(PPh2NR)2 in order to investigate the possible formation of dianionic bis(diphenyliminophosphorano)methanediides of the general type [C(PPh2NR)2]2−, which have been shown in the past decade to be suitable ligands for the stabilization of metal carbene complexes.21 Mononuclear carbene complexes containing a formal MC double bond have been realized with several metals, including group 2 metals,22 group 3 metals,23 group 4 metals,24 and group 14 metals25 as well as Bi26 and U and Ce.27 In addition, a few dinuclear metal complexes of the general type [C(PPh2NR)2](MR)2, in which two metal atoms are bonded to one bis(diphenyliminophosphorano)-

Figure 1. Solid-state structure of 1. H atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level.

Compound 1 forms a monomeric complex in the solid state with a trigonal-planar coordinated Be atom (sum of the bond angles 359.8(2)°). A slightly distorted boat-type conformation was observed for the CP2N2Be metallacycle, as was previously reported for comparable zinc complexes of the general types LZnMe,18 L2Zn2, and Cp*Zn-ZnL.19 The Be−N bond lengths in 1 (1.654(2), 1.667(2) Å) are comparable to those reported for β-diketiminate beryllium complexes, which were found to range from 1.58 to 1.70 Å,13 while beryllium amidinate complexes containing four-membered BeN2C rings showed slightly elongated Be−N bonds (1.73−1.75 Å),12 most likely due to the increased ring strain in comparison to the sixmembered BeN 2 C 3 and BeN 2 P 2 C rings. The P−N B


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Organometallics methanediide ligand, containing alkali metals, aluminum, zinc, and lanthanum have been structurally characterized,28−31 while to the best of our knowledge, analogous dinuclear group 2 metal carbene complexes are unknown, to date. Only dimeric dicalcium and dibarium dicarbene complexes have been reported by Harder et al., respectively.22 We therefore investigated the equimolar reaction of H2C(PPh2N-2,6-i-Pr2C6H3)2 with BeEt2 at higher temperatures, but we could not observe the formation of a beryllium carbene complex. We then turned our attention to reactions of H2C[PPh2NR]2 (R = SiMe3, Ph, 2,6-i-Pr2C6H3) with 2 equiv of BeEt2. While the reaction of H2C(PPh2N-2,6-i-Pr2C6H3)2 containing the sterically most demanding DIPP substituent with even 3 equiv of BeEt2 only resulted in the formation of [CH(PPh2N-2,6-i-Pr2C6H3)2]BeEt (1), the reactions of H2C[PPh2NR]2 (R = SiMe3, Ph) with 2 equiv of BeEt2 gave the corresponding binuclear bis(diphenylphosphinimino)methanediide beryllium complexes [C(PPh2NR)2](BeEt)2 (R = SiMe3 (2), Ph (3)), respectively (Scheme 2). In contrast to the monometalated derivatives as described before, 2 and 3 are stable in solution at ambient temperature.

Scheme 3. Binding Modes Observed for the Dianionic Bis(diphenylphosphinimino)methanediide Ligand

molecule in the asymmetric unit. Figures 2 and 3 show the solid-state structures of 2 and 3.

Scheme 2. Synthesis of 2 and 3

Only a single resonance was observed for the N-substituents (SiMe3, Ph) in 2 and 3. The 13C{1H} NMR spectra of 2 and 3 do not show any resonance of the quaternary PCP carbon atom even after long acquisition times. Comparable findings have been previously reported for the corresponding aluminum complexes and have been explained by the absence of nearby protons and, as a consequence, a bad magnetization transfer, as well as by broadening of the resonance due to coupling to two Al (I = 5/2) nuclei.28a,c Coupling of the methine carbon to two Be nuclei (I = 3/2) obviously has the same effect. In addition, the corresponding Li complexes also did not show the 13C resonance of the quaternary PCP carbon atom as a result of the same quadrupolar effect. These findings clearly underline the close relationship of Li and Be. Bis(diphenylphosphinimino)methanediides have been shown in the past to adopt either the so-called U form (A), typically observed with lithium as well as in case of zinc,28,30 or the W form (B), as was reported for aluminum and lanthanum complexes.29,31 Both isomeric forms are shown in Scheme 3. We therefore became interested in the solid-state structures of 2 and 3. Crystals of 2 and 3 suitable for single-crystal X-ray diffraction studies were obtained upon slow recrystallization from solutions of 2 and 3 in toluene at ambient temperature. 2 crystallizes in the triclinic space group P1̅ with two independent molecules in the asymmetric unit, while 3 crystallizes in the orthorhombic space group Pbca with one independent

Figure 2. Solid-state structure of 2. H atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level. The orientation of the molecules does not resemble their orientation in the asymmetric unit.

The backbone carbon atoms (Cbb) of the starting bis(diphenylphosphinimino)methane ligands are doubly deprotonated, resulting in the formation of methanediide fragments which adopt the W isomeric form in the solid state of both 2 and 3. The Be cations are coordinated by the methanediide ligand in a Cbb/N-chelating mode, resulting in two spirocyclic four-membered BeNPCbb rings (rms deviation from the best plane less than 0.07 Å in all cases). The interplanar angles of 66.3(2) and 60.2(2)° (2) and 59.07(8)° (3) and their tilt (N··· Cbb···N: 153.1(2) and 150.1(2)° (2); 153.5(1)° (3)) result in a strong distortion of the tetrahedral environment of the methanediide carbon atoms Cbb (Table 1). The Be−Cet bonds (1.724(5) Å, 2; 1.725 Å, 3) are significantly shorter than the Be−Cbb bond lengths (1.827(5), 1.828(4), 1.817(5), C


Organometallics

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Article

EXPERIMENTAL SECTION

General Procedures. Caution! Beryllium and its compounds are regarded as highly toxic and carcinogenic and have allergic potential when inhaled, with the risk of causing chronic beryllium disease (CBD).34 They should therefore be handled with appropriate safety precautions. All manipulations were performed in a glovebox (MBraun) under an Ar atmosphere or with standard Schlenk techniques. Solvents were carefully dried over Na/K and degassed prior to use. Bis(diphenylphosphinimino)methanes35 and BeEt236 were prepared according to literature procedures. NMR spectra were recorded on a Bruker Avance 300 spectrometer at 25 °C at 300 MHz (1H), 42 MHz (9Be), 75 MHz (13C), and 121 MHz (31P), respectively, and referenced to internal C6D5H (1H, δ 7.154; 13C, δ 128.0). IR spectra were recorded on a Bruker ALPHA-T FT-IR spectrometer equipped with a single-reflection ATR sampling module. Melting points were measured in sealed capillaries and were not corrected. Elemental analyses were not determined due to the expected toxicity of 1−3. Their purity was checked by NMR spectroscopy. [CH(PPh2N-2,6-i-Pr2C6H3)2]BeEt (1). A 0.20 g (0.35 mmol) amount of H2C(PPh2N-2,6-i-Pr2C6H3)2 was dissolved in 15 mL of toluene at −78 °C, and 0.024 g (0.35 mmol) of BeEt2 was added via syringe to the pale orange solution. The solution was warmed to ambient temperature overnight. The solvent was removed under vacuum, and the resulting crude product was washed with cold pentane. Recrystallization of the remaining solid in a minimum amount of toluene at 20 °C yielded colorless crystals within 24 h. Yield: 0.25 g (93%). Mp: >220 °C dec. 1H NMR (300 MHz, C6D6, 25 °C): δ −0.24 (quart, 2H, 3JHH = 8.3 Hz, BeCH2CH3), 0.48 (d, 12H, 3 JHH = 6.9 Hz, CH(CH3)2), 0.50 (t, 3H, 3JHH = 8.2 Hz, BeCH2CH3), 1.02 (s, 1H, PCHP), 1.48 (d, 12H, 3JHH = 6.9 Hz, H(CH3)2), 3.78 (sept, 4H, 3JHH = 6.8, CH(CH3)2), 6.89−7.20 (m, 18H, Ph2P, 2,6-iPr2-C6H3), 7.53−7.59 (m, 8H, o-Ph2P). 13C NMR (75 MHz, C6D6, 25 °C): δ 11.3 (BeCH2CH3), 12.2 (BeCH2CH3), 23.3 (PCHP), 25.4 (CH(CH3)2), 29.3 (CH(CH3)2), 124.3 (p-PhP), 125.5 (p-PhN), 127.3 (m-PhP), 128.9 (m-PhN), 130.6 (o-PhN), 133.2 (t, 2JCP = 4.8 Hz, o-PhP), 142.2 (t, 1JCP = 4.5 Hz, i-PhP), 147.3 (t, 2JCP = 2.6 Hz, i-PhN). 9Be NMR (300 MHz, C6D6, 25 °C): δ 15.62. 31P NMR (300 MHz, C6D6, 25 °C): δ 29.95. ATR-IR: ν̃ 3052, 2961, 2946, 2924, 2865, 2846, 1588, 1576, 1456, 1382, 1361, 1316, 1238, 1177, 1097, 1042, 1027, 1008, 989, 949, 925, 892, 822, 803, 725, 691, 676, 607, 546, 501, 485, 450, 390 cm−1. General Synthesis of [C(PPh2NR)2]Be2Et2. H2C(PPh2NR)2 (R = SiMe3, 0.20 g, 0.36 mmol; R = Ph, 0.20 g, 0.48 mmol) was dissolved in 15 mL of toluene at −78 °C, and a 2-fold amount of BeEt2 (0.048 g, 0.72 mmol; 0.064 g, 0.96 mmol) was added via syringe to the solution. The solution was warmed to ambient temperature within 12 h. The solvent was removed under vacuum, and the crude product was washed with cold pentane. Recrystallization of the remaining solid in a minimum amount of toluene at 20 °C yielded colorless crystals within 24 h. [C(PPh2NSiMe3)2](BeEt)2 (2). Yield: 0.21 g (90%). Mp: >220 °C dec. 1H NMR (300 MHz, C6D6, 25 °C): δ 0.10 (s, 18H, SiMe3), 0.55− 0.74 (2 quart, 4H, 3JHH = 8.0 Hz, BeCH2CH3), 1.67 (t, 6H, 3JHH = 8.2 Hz, BeCH2CH3), 6.73−6.80 (m, 4H, Ph), 6.87−6.94 (m, 2H, Ph), 7.03−7.09 (m, 6H, Ph), 7.18−7.26 (m, 4H, Ph), 7.55−7.62 (m, 4H, oPh2P). 13C NMR (75 MHz, C6D6, 25 °C): δ 3.0 (SiMe3), 4.2 (BeCH2CH3), 12.2 (BeCH2CH3), 128.4−128.7 (m, m-PhP), 131.5 (mPhN), 131.7 (o-PhP), 132.3−132.5 (dt, 3JCP = 5.9, o-PhN), 134.7 (i-PhP), 135.9 (i-PhN). 9Be NMR (300 MHz, C6D6, 25 °C): δ 0.93. 31P NMR (300 MHz, C6D6, 25 °C): δ 28.06. ATR-IR: ν̃ 3058, 2955, 2932, 2894, 2854, 2838, 1590, 1482, 1454, 1435, 1408, 1309, 1245, 1227, 1191, 1133, 1111, 1083, 1026, 990, 955, 916, 833, 791, 770, 744, 721, 668, 621, 595, 564, 529, 507, 457, 427, 384 cm−1. [C(PPh2NPh)2](BeEt)2 (3). Yield: 0.28 g (87%). Mp: >220 °C dec. 1 H NMR (300 MHz, C6D6, 25 °C): δ 0.81−0.84 (2 quart, 4H, 3JHH = 8.0 Hz, BeCH2CH3), 1.70 (t, 6H, 3JHH = 8.2 Hz, BeCH2CH3), 6.65− 6.74 (m, 6H, Ph), 6.86−7.00 (m, 12H, Ph), 7.12 (m, 4H, Ph), 7.56− 7.64 (m, 4H, o-Ph2P). 13C NMR (75 MHz, C6D6, 25 °C): δ 3.7 (BeCH2CH3), 12.0 (BeCH2CH3), 121.8 (t, 4JCP = 7.0, p-PhP), 128.7

Figure 3. Solid-state structure of 3. H atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level.

1.842(5) Å, 2; 1.841(3), 1.827(3) Å, 3) but are comparable to that observed in 1 (1.753(2) Å). The short P−Cbb (1.807(3) Å, 2; 1.715 Å, 3) and P−N bond lengths (1.620(2) Å, 2; 1.638 Å, 3) are also comparable to those in 1 and indicate delocalized πelectron systems with pronounced double-bonding character throughout the whole backbone of the ligands, as was previously observed in bis(diphenylphosphinimino)methanediide complexes.28−30 The sp2 hybridization at the N atoms, which is necessary for the π-bonding, is confirmed by the trigonal-planar coordination sphere of the N atoms (all sums of the bond angles larger than 358°). The exocyclic P− Cbb−P bond angles (134.29(16)°, 2; 128.87(11)°, 3), which are significantly larger than the exocyclic Be1−C1−Be2 bond angles (94.7(2)°, 2; 91.11(14)°, 3), are comparable to the endocyclic P−Cbb−P bond angle in 1 (129.53(8)°), while the endocyclic Cbb−P−N bond angles (average values: 97.48(13)°, 2; 94.28(9)°, 3) are significantly smaller in comparison to those of 1 (109.95(7)°), most likely resulting from the smaller ring size. Short Be−Be distances of 2.687(5) Å (2) and 2.619(4) Å (3) are observed, which clearly exceed the sum of the covalent radii (2.04 Å)32 but are well below the sum of the van der Waals radii (3.06 Å).33

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CONCLUSION Bis(diphenylphosphinimino)methanide beryllium complexes were formed in ethane elimination reactions between equimolar amounts of H2C(PPh2NR)2 and BeEt2, but only [CH(PPh2N2,6-i-Pr2C6H3)2]BeEt (1) was found to be stable at ambient temperature. In addition, reactions of H2C(PPh2NR)2 with 2 equiv of BeEt2 yielded the first bis(diphenylphosphinimino)methanediide complexes [C(PPh2NSiMe3)2](BeEt)2 (2) and [C(PPh2NPh)2](BeEt)2 (3), while the reaction of H2C(PPh2N-2,6-i-Pr2C6H3)2 containing the sterically most demanding N substituent with even 3 equiv of BeEt2 only gave 1. These studies clearly prove the strong deprotonating properties of BeEt2, which are comparable to those of lithium alkyls and aluminum alkyls. In remarkable contrast to the results from 2fold deprotonation reactions of H2C(PPh2NR)2 with calcium and barium complexes, which yielded dimeric dimetal dicarbene complexes, the reactions with BeEt2 also occurred with 2-fold deprotonation but formation of dinuclear complexes 2 and 3, which are without precedence in group 2 metal chemistry. D


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Organometallics (m-PhP), 128.8−129.0 (dt, 4JCP = 5.6 Hz, m-PhN), 129.7 (o-PhP), 132.0 (o-PhN), 132.8−132.9 (dt, 1JCP = 5.4 Hz, i-PhP), 146.3 (i-PhN). 9Be NMR (300 MHz, C6D6, 25 °C): δ 19.23. 31P NMR (300 MHz, C6D6, 25 °C): δ 29.32. ATR-IR: ν̃ 3054, 3034, 2924, 2887, 2850, 2775, 2717, 1592, 1572, 1486, 1434, 1310, 1274, 1141, 175, 1015, 980, 809, 788, 755, 740, 719, 690, 604, 561, 522, 504, 484, 448, 381 cm−1. Single-Crystal X-ray Analyses. Crystallographic data of 1−3, which were collected on a Bruker AXS APEX 2 diffractometer (Mo Kα radiation, λ = 0.71073 Å), are summarized in Table S1 in the Supporting Information, while central bond lengths and angles are summarized in Table 1. Figures 1−3 show diagrams of the solid-state structures of 1−3. Data were collected at 100(1) K. The structures were solved by direct methods (SHELXS-97) and refined anisotropically by full-matrix least squares on F2 (SHELXL2014).37 Absorption corrections were performed semiempirically from equivalent reflections on the basis of multiscans (Bruker AXS APEX2, TWINABS). 1 was a nonmerohedrally twinned crystal, and the structure model was refined against detwinned HKLF4 data. 2 was pseudomerohedrally twinned by a 2-fold rotational axis parallel to b. Crystallographic data of 1−3 (excluding structure factors) have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC-1478801 (1), CCDC-1478803 (2), and CCDC-1478802 (3). Copies of the data can be obtained free of charge on application to the CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (fax, (+44) 1223/336033; e-mail, [email protected]).

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.6b00380. 1 H, 9Be, 13C, and 31P NMR and IR spectra as well as the crystallographic details of 1−3 (PDF) X-ray crystallographic data of 1−3 (CIF)

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AUTHOR INFORMATION

Corresponding Author

*S.S.: tel, +49 0201-1834635; fax, + 49 0201-1833830; e-mail, [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS S.S. thanks the University of Duisburg-Essen for financial support and Materion Co. for providing beryllium metal. REFERENCES

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